DOCSLIB.ORG

Chromospheric Activity, Lithium and Radial Velocities of Single Late-Type Stars Possible Members of Young Moving Groups ⋆ ⋆⋆

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Chromospheric Activity, Lithium and Radial Velocities of Single Late-Type Stars Possible Members of Young Moving Groups ⋆ ⋆⋆ 1 Abstract. We present here high resolution echelle spec- tra taken during three observing runs of 14 single late- type stars identified in our previous studies (Montes et al. 2001b, hereafter Paper I) as possible members of differ- ent young stellar kinematic groups (Local Association (20 - 150 Myr), Ursa Major group (300 Myr), Hyades super- cluster (600 Myr), and IC 2391 supercluster (35 Myr)). Radial velocities have been determined by cross correla- tion with radial velocity standard stars and used together with precise measurements of proper motions and paral- laxes taken from Hipparcos and Tycho-2 Catalogues, to calculate Galactic space motions (U, V , W ) and to ap- ply Eggen’s kinematic criteria. The chromospheric activ- ity level of these stars have been analysed using the in- formation provided for several optical spectroscopic fea- tures (from the Ca ii H & K to Ca ii IRT lines) that are formed at different heights in the chromosphere. The Li i λ6707.8 A˚ line equivalent width (EW) has been de- termined and compared in the EW (Li i) versus spectral type diagram with the EW (Li i) of stars members of well- known young open clusters of different ages, in order to ob- tain an age estimation. All these data allow us to analyse in more detail the membership of these stars in the differ- ent young stellar kinematic groups. Using both, kinematic and spectroscopic criteria we have confirmed PW And, V368 Cep, V383 Lac, EP Eri, DX Leo, HD 77407, and EK Dra as members of the Local Association and V834 Tau, π1 UMa, and GJ 503.2 as members of the Ursa Ma- jor group. A clear rotation-activity dependence has been found in these stars. Key words: stars: activity – stars: chromospheres – stars: late-type – stars: abundances – stars: kinematic – open clusters and associations: general arXiv:astro-ph/0110066v1 2 Oct 2001 A&A manuscript no. ASTRONOMY (will be inserted by hand later) AND Your thesaurus codes are: missing; you have not inserted them ASTROPHYSICS Chromospheric activity, lithium and radial velocities of single late-type stars possible members of young moving groups ⋆ ⋆⋆ D. Montes, J. L´opez-Santiago, M.J. Fern´andez-Figueroa, and M.C. G´alvez Departamento de Astrof´ısica, Facultad de Ciencias F´ısicas, Universidad Complutense de Madrid, E-28040 Madrid, Spain E-mail: dmg@astrax.fis.ucm.es Received 23 July 2001 / Accepted 26 September 2001 1. Introduction could lead to a better understanding of star formation history in the solar neighbourhood. In our previous work It has long been known that in the solar vicinity there are (Montes et al. 2000a, 2001a; Paper I) a sample of late-type several kinematic groups of stars that share the space mo- stars of previously established members and possible new tions of well-known open clusters. Eggen (1994) defined a candidates to these five young SKG have been identified. ”supercluster” (SC) as a group of stars, gravitationally un- In order to better establish the membership of these can- bound, that share the same kinematics and may occupy didate stars in the different young SKG, we have started extended regions in the Galaxy, and a ”moving group” a program of high resolution echelle spectroscopic obser- (MG) as the part of the supercluster that enters the so- vations. The spectroscopic analysis of these stars allows lar neighbourhood and can be observed all over the sky. us to obtain a better determination of their radial veloc- The origin of these stellar kinematic groups (SKG) could ity, lithium (λ6707.8 line) equivalent width , rotational be the evaporation of an open cluster, the remnants of a velocity and the level of chromospheric activity. We will star formation region or a juxtaposition of several little use all these new data to study in detail the kinematics star formation bursts at different epochs in adjacent cells (Galactic space motions (U, V , W )) of these stars, apply of the velocity field. The youngest and best-documented age-dating methods for late-type stars, and in this way SKG are: the Hyades supercluster (600 Myr) the Ursa Ma- analyse in more detail the membership of these stars in jor group (Sirius supercluster) (300 Myr), the Local As- the different SKG. sociation or Pleiades moving group (20 to 150 Myr), the We present here the results of our first spectroscopy IC 2391 supercluster (35-55 Myr), and the Castor mov- studies of a sample of 14 single late-type stars selected ing group (200 Myr) (see Montes et al. 2001b, hereafter by us in Paper I as young disk stars or possible members Paper I, and references therein). of some of the above mentioned young SKG. The high Well-known members of these SKG are mainly early- resolution echelle spectra analysed here were taken dur- type stars and few studies have been centered on late-type ing three observing runs (from 1999 to 2000) and include stars. However, the identification of a significant number all the optical chromospheric activity indicators from the of late-type population in these young SKG is extremely Ca ii H&KtoCa ii IRT lines as well as the Li i λ6707.8 important for the study of the chromospheric activity and line. In Sect. 2 we give the details of our observations and Send offprint requests to: D. Montes ⋆ data reduction. The radial velocity and Galactic space- Based on observations made with the 2.2m telescope of the velocity components (U, V , W ) determination is described German-Spanish Astronomical Centre, Calar Alto (Almer´ıa, i Spain), operated by the Max-Planck-Institute for Astronomy, in Sect. 3. The Li λ6707.8 line is analysed in Sect. 4. The Heidelberg, jointly with the Spanish National Commission for different chromospheric activity indicators are analysed in Astronomy, with the Nordic Optical Telescope (NOT), oper- Sect. 5. Individual results for each star are reported in ated on the island of La Palma jointly by Denmark, Finland, Sect. 6. Finally, in Sect. 7 the discussion and conclusions Iceland, Norway and Sweden, in the Spanish Observatorio del are given. Roque de Los Muchachos of the Instituto de Astrof´ısica de Canarias, and with the Isaac Newton Telescope (INT) oper- ated on the island of La Palma by the Isaac Newton Group in 2. Observations and Data Reduction the Spanish Observatorio del Roque de Los Muchachos of the Instituto de Astrof´ısica de Canarias. The spectroscopic echelle observations of the stars anal- ⋆⋆ Tables 1, 4, 5 also available in electronic form ysed in this paper were obtained during three observing Correspondence to: dmg@astrax.fis.ucm.es runs: D. Montes et al.: Spectroscopic analysis of single late-type stars members of young moving groups 3 Fig. 1. (U, V ) and (W , V ) planes (Boettlinger Diagram) for our star sample. We plot with different symbols the stars belonging to the different stellar kinematic groups. Filled symbols are stars that satisfied both of Eggen’s criteria (peculiar velocity, P V , and radial velocity, ρc), open symbols are other possible members. Big crosses are plotted in the central position of each group. The dashed line represents the boundaries that determine the young disk population as defined by Eggen (1984a, 1989). 1) 2.2m-FOCES 1999/07 ESA-MUSICOS spectrograph. This is a fibre-fed cross- This took place on 24 -29 July 1999 using the 2.2 m tele- dispersed echelle spectrograph, built as a replica of the scope at the German Spanish Astronomical Observatory first MUSICOS spectrograph (Baudrand & B¨ohm 1992) (CAHA) (Almer´ıa, Spain). The Fibre Optics Cassegrain and developed as part of MUlti-SIte COntinuous Spec- Echelle Spectrograph (FOCES) (Pfeiffer et al. 1998) was troscopy (MUSICOS1) project. During this observing run, used with a 20482 15µ LORAL#11i CCD detector. The a 10242 24µ TEK5 CCD detector was used, obtaining wavelength range covers from 3910 to 9075 A˚ in 84 orders. wavelength coverage from 4430 A˚ to 10225 A˚ in 73 or- The reciprocal dispersion ranges from 0.03 to 0.07 A/pixel˚ ders. The reciprocal dispersion ranges from 0.07 to 0.15 and the spectral resolution, determined as the full width A˚ and the spectral resolution (FWHM) from 0.16 to 0.30 at half maximum (FWHM) of the arc comparison lines, A.˚ ranges from 0.09 to 0.26 A.˚ The sample of late-type stars analysed in this paper 2) NOT-SOFIN 1999/11 as well as the the non-active stars used as reference stars Observations taken on 26 -27 November 1999 using the in the spectral subtraction and the radial velocity stan- 2.56 m Nordic Optical Telescope (NOT) located at the dards used in the radial velocity determinations are listed Observatorio del Roque de Los Muchachos (La Palma, in Tables 1 and 2. In Table 1 we give the observing log. Spain). The Soviet Finnish High Resolution Echelle Spec- For each observation we list date, UT and the signal to ii trograph (SOFIN) was used with an echelle grating (79 noise ratio (S/N) obtained in the Ca H&KandHα line grooves/mm), Astromed-3200 camera and a 1152×770 regions. Table 2 shows the name, HD number, and other pixel EEV P88200 CCD detector. The wavelength range stellar parameters such as the spectral type (Tsp), color covers from 3525 to 10425 A˚ in 44 orders. The recipro- indexes V –R and B–V , rotational velocity (v sin i), rota- cal dispersion ranges from 0.06 to 0.17 A/pixel˚ and the tional period (Pphot). The V –R and B–V color indexes spectral resolution (FWHM) from 0.14 to 0.32 A.˚ are obtained from the relation with spectral type given by Landolt-B¨ornstein (Schmidt-Kaler 1982) when individual 3) INT-MUSICOS 2000/01 values are not given in the literature.
Load more

Recommended publications
  • Target Selection for the SUNS and DEBRIS Surveys for Debris Discs in the Solar Neighbourhood
    Mon. Not. R. Astron. Soc. 000, 1–?? (2009) Printed 18 November 2009 (MN LATEX style file v2.2) Target selection for the SUNS and DEBRIS surveys for debris discs in the solar neighbourhood N. M. Phillips1, J. S. Greaves2, W. R. F. Dent3, B. C. Matthews4 W. S. Holland3, M. C. Wyatt5, B. Sibthorpe3 1Institute for Astronomy (IfA), Royal Observatory Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ 2School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife, KY16 9SS 3UK Astronomy Technology Centre (UKATC), Royal Observatory Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ 4Herzberg Institute of Astrophysics (HIA), National Research Council of Canada, Victoria, BC, Canada 5Institute of Astronomy (IoA), University of Cambridge, Madingley Road, Cambridge, CB3 0HA Accepted 2009 September 2. Received 2009 July 27; in original form 2009 March 31 ABSTRACT Debris discs – analogous to the Asteroid and Kuiper-Edgeworth belts in the Solar system – have so far mostly been identified and studied in thermal emission shortward of 100 µm. The Herschel space observatory and the SCUBA-2 camera on the James Clerk Maxwell Telescope will allow efficient photometric surveying at 70 to 850 µm, which allow for the detection of cooler discs not yet discovered, and the measurement of disc masses and temperatures when combined with shorter wavelength photometry. The SCUBA-2 Unbiased Nearby Stars (SUNS) survey and the DEBRIS Herschel Open Time Key Project are complimentary legacy surveys observing samples of ∼500 nearby stellar systems. To maximise the legacy value of these surveys, great care has gone into the target selection process. This paper describes the target selection process and presents the target lists of these two surveys.
    [Show full text]
  • Evidence of Intra-Binary Shock Emission from the Redback Pulsar PSR J1048+2339? A
    Astronomy & Astrophysics manuscript no. J1048 ©ESO 2021 March 12, 2021 Evidence of intra-binary shock emission from the redback pulsar PSR J1048+2339? A. Miraval Zanon1;2, P. D’Avanzo2, A. Ridolfi3;4, F. Coti Zelati5;6;2, S. Campana2, C. Tiburzi7, D. de Martino8, T. Munoz˜ Darias9, C.G. Bassa7, L. Zampieri10, A. Possenti3;11, F. Ambrosino12;13;14, A. Papitto12, M. C. Baglio15;2, M. Burgay3, A. Burtovoi16;10, D. Michilli17;7;18;19, P.Ochner20;10, P. Zucca7 1 Università dell’Insubria, Dipartimento di Scienza e Alta Tecnologia, Via Valleggio 11, I-22100, Como, Italy 2 INAF, Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807, Merate (LC), Italy e-mail: [email protected] 3 INAF, Osservatorio Astronomico di Cagliari, Via della Scienza 5, I-09047, Selargius (CA), Italy 4 Max-Planck-Institut fur¨ Radioastronomie, Auf dem Hugel¨ 69, D-53121, Bonn, Germany 5 Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans s/n, 08193, Barcelona, Spain 6 Institut d’Estudis Espacials de Catalunya (IEEC), Carrer Gran Capità 2–4, 08034, Barcelona, Spain 7 ASTRON, The Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD, Dwingeloo, the Netherlands 8 INAF, Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80131, Napoli, Italy 9 Instituto de Astrofisica de Canarias, Via Lactea, La Laguna E-38200, Santa Cruz de Tenerife, Spain 10 INAF, Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122, Padova, Italy 11 Università degli Studi di Cagliari, Dipartimento di Fisica, S.P. Monserrato-Sestu km 0,700, I-09042 Monserrato (CA), Italy 12 INAF, Osservatorio Astronomico di Roma, Via Frascati 33, I-00078, Monteporzio Catone (Roma), Italy 13 INAF, Istituto di Astrofisica e Planetologia Spaziali, Via Fosso del Cavaliere 100, I-00133, Roma, Italy 14 Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185, Roma, Italy 15 Center for Astro, Particle and Planetary Physics, New York University Abu Dhabi, PO Box 129188, Abu Dhabi, UAE 16 Center of Studies and Activities for Space (CISAS) ‘G.
    [Show full text]
  • Basics of Astrophysics Revisited. I. Mass- Luminosity Relation for K, M and G Class Stars
    Basics of astrophysics revisited. I. Mass- luminosity relation for K, M and G class stars Edgars Alksnis [email protected] Small volume statistics show, that luminosity of slow rotating stars is proportional to their angular momentums of rotation. Cause should be outside of standard solar model. Slow rotating giants and dim dwarfs are not out of „main sequence” in this concept. Predictive power of stellar mass-radius- equatorial rotation speed-luminosity relation has been offered to test in numerous examples. Keywords: mass-luminosity relation, stellar rotation, stellar mass prediction, stellar rotation prediction ...Such vibrations would proceed from deep inside the sun. They are a fast way of transporting large amounts of energy from the interior to the surface that is not envisioned in present theory.... They could stir up the material inside the sun, which current theory tends to see as well layered, and that could affect the fusion dynamics. If they come to be generally accepted, they will require a reworking of solar theory, and that carries in its train a reworking of stellar theory generally. These vibrations could reverberate throughout astronomy. (Science News, Vol. 115, April 21, 1979, p. 270). Actual expression for stellar mass-luminosity relation (fig.1) Fig.1 Stellar mass- luminosity relation. Credit: Ay20. L- luminosity, relative to the Sun, M- mass, relative to the Sun. remain empiric and in fact contain unresolvable contradiction: stellar luminosity basically is connected with their surface area (radius squared) but mass (radius in cube) appears as a factor which generate luminosity. That purely geometric difference had pressed astrophysicists to place several classes of stars outside of „main sequence” in the frame of their strange theoretic constructions.
    [Show full text]
  • Activity Trends in Young Solar-Type Stars
    Astronomy & Astrophysics manuscript no. solan c ESO 2018 September 12, 2018 Activity trends in young solar-type stars ⋆,⋆⋆ J. Lehtinen1, L. Jetsu1, T. Hackman1, P. Kajatkari1, and G.W. Henry2 1 Department of Physics, PO Box 64, 00014 University of Helsinki, 00014 Helsinki, Finland e-mail: [email protected] 2 Center of Excellence in Information Systems, Tennessee State University, 3500 John A. Merritt Blvd., Box 9501, Nashville, TN 37209, USA Received date / Accepted date ABSTRACT Aims. We study a sample of 21 young and active solar-type stars with spectral types ranging from late F to mid K and characterize the behaviour of their activity. Methods. We apply the continuous period search (CPS) time series analysis method on Johnson B- and V-band photometry of the sample stars, collected over a period of 16 to 27 years. Using the CPS method, we estimate the surface differential rotation and determine the existence and behaviour of active longitudes and activity cycles on the stars. We supplement the time series results by ′ ′ 4 calculating new log RHK = log FHK /σTeff emission indices for the stars from high resolution spectroscopy. Results. The measurements of the photometric rotation period variations reveal a positive correlation between the relative differential 1.36 rotation coefficient and the rotation period as k ∝ Prot , but do not reveal any dependence of the differential rotation on the effective temperature of the stars. Secondary period searches reveal activity cycles in 18 of the stars and temporary or persistent active lon- −1 gitudes in 11 of them. The activity cycles fall into specific activity branches when examined in the log Prot/Pcyc vs.
    [Show full text]
  • Activity Trends in Young Solar-Type Stars,
    A&A 588, A38 (2016) Astronomy DOI: 10.1051/0004-6361/201527420 & c ESO 2016 Astrophysics Activity trends in young solar-type stars, J. Lehtinen1, L. Jetsu1, T. Hackman1,P.Kajatkari1, and G. W. Henry2 1 Department of Physics, PO Box 64, 00014 University of Helsinki, 00014 Helsinki, Finland e-mail: [email protected] 2 Center of Excellence in Information Systems, Tennessee State University, 3500 John A. Merritt Blvd., Box 9501, Nashville, TN 37209, USA Received 22 September 2015 / Accepted 7 December 2015 ABSTRACT Aims. We study a sample of 21 young and active solar-type stars with spectral types ranging from late F to mid K and characterize the behaviour of their activity. Methods. We apply the continuous period search (CPS) time series analysis method on Johnson B-andV-band photometry of the sample stars, collected over a period of 16 to 27 years. Using the CPS method, we estimate the surface differential rotation and de- termine the existence and behaviour of active longitudes and activity cycles on the stars. We supplement the time series results by = /σ 4 calculating new log RHK log FHK Teff emission indices for the stars from high resolution spectroscopy. Results. The measurements of the photometric rotation period variations reveal a positive correlation between the relative differential ffi ∝ 1.36 ff ff rotation coe cient and the rotation period as k Prot , but do not reveal any dependence of the di erential rotation on the e ective temperature of the stars. Secondary period searches reveal activity cycles in 18 of the stars and temporary or persistent active lon- −1 gitudes in 11 of them.
    [Show full text]
  • Astronomy & Astrophysics Chromospheric Activity, Lithium And
    A&A 379, 976–991 (2001) Astronomy DOI: 10.1051/0004-6361:20011385 & c ESO 2001 Astrophysics Chromospheric activity, lithium and radial velocities of single late-type stars possible members of young moving groups?,?? D. Montes, J. L´opez-Santiago, M. J. Fern´andez-Figueroa, and M. C. G´alvez Departamento de Astrof´ısica, Facultad de Ciencias F´ısicas, Universidad Complutense de Madrid, 28040 Madrid, Spain Received 23 July 2001 / Accepted 26 September 2001 Abstract. We present here high resolution echelle spectra taken during three observing runs of 14 single late- type stars identified in our previous studies (Montes et al. 2001b, hereafter Paper I) as possible members of different young stellar kinematic groups (Local Association (20–150 Myr), Ursa Major group (300 Myr), Hyades supercluster (600 Myr), and IC 2391 supercluster (35 Myr)). Radial velocities have been determined by cross correlation with radial velocity standard stars and used together with precise measurements of proper motions and parallaxes taken from Hipparcos and Tycho-2 Catalogues, to calculate Galactic space motions (U, V , W ) and to apply Eggen’s kinematic criteria. The chromospheric activity level of these stars have been analysed using the information provided for several optical spectroscopic features (from the Ca ii H&KtoCaii IRT lines) that are formed at different heights in the chromosphere. The Li i λ6707.8 A˚ line equivalent width (EW) has been determinedandcomparedintheEW(Li i) versus spectral type diagram with the EW(Li i) of stars members of well-known young open clusters of different ages, in order to obtain an age estimation. All these data allow us to analyse in more detail the membership of these stars in the different young stellar kinematic groups.
    [Show full text]
  • An Infrared Coronagraphic Survey for Substellar Companions
    An Infrared Coronagraphic Survey for Substellar Companions Patrick J. Lowrance1, E. E. Becklin2, Glenn Schneider3, J. Davy Kirkpatrick4, Alycia J. Weinberger5, B. Zuckerman2, Christophe Dumas6, Jean-Luc Beuzit7, Phil Plait8, Eliot Malumuth9, Sally Heap9, Richard J. Terrile10, Dean C. Hines11 ABSTRACT We have used the F160W filter (1.4 − 1.8 µm) and the coronagraph on the Near- InfraRed Camera and Multi-Object Spectrometer (NICMOS) on the Hubble Space Tele- scope (HST) to survey 45 single stars with a median age of 0.15 Gyr, an average distance of 30 pc, and an average H-magnitude of 7 mag. For the median age we were capable of detecting a 30 MJupiter companion at separations between 15 and 200 AU. A 5 MJupiter object could have been detected at 30 AU around 36% of our primaries. For several of our targets that were less than 30 Myr old, the lower mass limit was as low as a Jupiter mass, well into the high mass planet region. Results of the entire survey include the proper motion verification of five low-mass stellar companions, two brown dwarfs (HR7329B and TWA5B) and one possible brown dwarf binary (Gl 577B/C). Subject headings: stars:low-mass,brown dwarfs 1. Introduction Just over a decade ago substellar astronomy exploded in discoveries with the first brown dwarfs in the Pleiades (Rebolo, Zapatero Osorio & Martin 1995), the first ‘cool’ brown dwarf, Gl 1Spitzer Science Center, MS 220-6, California Institute of Technology, Pasadena, CA. 91125; arXiv:astro-ph/0506358v1 15 Jun 2005 [email protected] 2University of California Los Angeles,
    [Show full text]
  • Late-Type Members of Young Stellar Kinematic Groups – I. Single Stars
    Mon. Not. R. Astron. Soc. 328, 45–63 (2001) Late-type members of young stellar kinematic groups – I. Single stars D. Montes,P J. Lo´pez-Santiago, M. C. Ga´lvez, M. J. Ferna´ndez-Figueroa, E. De Castro and M. Cornide Departamento de Astrofı´sica, Facultad de Fı´sicas, Universidad Complutense de Madrid, E-28040 Madrid, Spain Accepted 2001 June 28. Received 2001 May 31; in original form 2001 February 5 ABSTRACT This is the first paper of a series aimed at studying the properties of late-type members of young stellar kinematic groups. We concentrate our study on classical young moving groups such as the Local Association (Pleiades moving group, 20–150 MyrÞ, IC 2391 supercluster (35 Myr), Ursa Major group (Sirius supercluster, 300 Myr), and Hyades supercluster (600 Myr), as well as on recently identified groups such as the Castor moving group (200 Myr). In this paper we compile a preliminary list of single late-type possible members of some of these young stellar kinematic groups. Stars are selected from previously established members of stellar kinematic groups based on photometric and kinematic properties as well as from candidates based on other criteria such as their level of chromospheric activity, rotation rate and lithium abundance. Precise measurements of proper motions and parallaxes taken from the Hipparcos Catalogue, as well as from the Tycho-2 Catalogue, and published radial velocity measurements are used to calculate the Galactic space motions (U, V, W ) and to apply Eggen’s kinematic criteria in order to determine the membership of the selected stars to the different groups.
    [Show full text]
  • 1995Aj 110.2926H the Astronomical Journal
    THE ASTRONOMICAL JOURNAL VOLUME 110, NUMBER 6 DECEMBER 1995 110.2926H AN AUTOMATED SEARCH FOR VARIABILITY IN CHROMOSPHERICALLY ACTIVE STARS Gregory W. Henry and Francis C. Fekel1 Center for Automated Space Science and Center of Excellence in Information Systems, Tennessee State University, 330 Tenth Avenue 1995AJ North, Nashville, Tennessee 37203-3401 Electronic mail: [email protected], [email protected] Douglas S. Hall Dyer Observatory, Vanderbilt University, Nashville, Tennessee 37235 Electronic mail: [email protected] Received 1995 August 9; revised 1995 September 5 ABSTRACT We have completed an automated photometric survey of 66 potential or known chromospherically active late-type stars with the 0.4 m Vanderbilt/Tennessee State robotic telescope. The precision of the observations from this telescope matches that predicted from photon and scintillation noise alone and represents a significant improvement in the precision of previous robotic telescope surveys of chromospherically active stars. Light variability has been detected and its period has been determined for 47 stars, 41 of which are newly discovered variables. The primary mechanism of variability is rotational modulation of a spotted surface. In addition we have detected eclipses in HD 62668 and HD 141690 and the ellipticity effect in HD 223971. The light variations of HD 181475 are the result of pulsation while the variability mechanism of HD 99267, a newly identified member of a small group of early-F stars, is so far unidentified. High-dispersion spectroscopic observations of all the variable stars also have been obtained and analyzed to determine spectral type, v sin /, and velocity variability for each star.
    [Show full text]
  • Chromospheric Activity, Lithium and Radial Velocities of Single Late-Type Stars Possible Members of Young Moving Groups?,??
    A&A 379, 976–991 (2001) Astronomy DOI: 10.1051/0004-6361:20011385 & c ESO 2001 Astrophysics Chromospheric activity, lithium and radial velocities of single late-type stars possible members of young moving groups?,?? D. Montes, J. L´opez-Santiago, M. J. Fern´andez-Figueroa, and M. C. G´alvez Departamento de Astrof´ısica, Facultad de Ciencias F´ısicas, Universidad Complutense de Madrid, 28040 Madrid, Spain Received 23 July 2001 / Accepted 26 September 2001 Abstract. We present here high resolution echelle spectra taken during three observing runs of 14 single late- type stars identified in our previous studies (Montes et al. 2001b, hereafter Paper I) as possible members of different young stellar kinematic groups (Local Association (20–150 Myr), Ursa Major group (300 Myr), Hyades supercluster (600 Myr), and IC 2391 supercluster (35 Myr)). Radial velocities have been determined by cross correlation with radial velocity standard stars and used together with precise measurements of proper motions and parallaxes taken from Hipparcos and Tycho-2 Catalogues, to calculate Galactic space motions (U, V , W ) and to apply Eggen’s kinematic criteria. The chromospheric activity level of these stars have been analysed using the information provided for several optical spectroscopic features (from the Ca ii H&KtoCaii IRT lines) that are formed at different heights in the chromosphere. The Li i λ6707.8 A˚ line equivalent width (EW) has been determinedandcomparedintheEW(Li i) versus spectral type diagram with the EW(Li i) of stars members of well-known young open clusters of different ages, in order to obtain an age estimation. All these data allow us to analyse in more detail the membership of these stars in the different young stellar kinematic groups.
    [Show full text]
  • Download This Article (Pdf)
    470 Index, JAAVSO Volume 35, 2007 Index to Volume 35 Author AAVSO Headquarters Supernova Search Committee Report 322, 468 Aerts, C., and C. Waelkens, P. De Cat, K. Kolenberg, E. Kestens, M. Grenon, et al. Pulsating B Stars Discovered by HIPPARCOS (Abstract) 58 Ak, T., and M. T. Özkan Statistical Analyses of the AAVSO Light Curves of Z Camelopardalis and AH Herculis (Abstract) 144 Ak, T., in M. T. Özkan et al. The UV Luminosity of Z Cam Type Dwarf Novae (Abstract) 148 Allakhverdiyev, A., in O. Guseinov et al. A Catalogue of X-Ray Binaries (Abstract) 158 Allen, William, in William Liller et al. Light and Color Curves of the Unusual Slow Nova LMC 2005 359 Amoretti, M., and M. Badiali, C. La Padula, D. Nanni, A. Preite-Martinez, A. Vignato, et al. The Three-Reflection, Two-Mirror Telescope (TRT): A Compact Instrument for Wide Field Astronomy (Abstract) 49 Andronov, I. L. Time Series Analysis of Amateur Observations: Various Methods and Some Results 204 Andronov, I. L., and L. L. Chinarova Non-Parametric Methods for Periodogram Analysis: Test Function Interrelations and Properties 201 Andronov, I. L., and L. S. Kudashkina Correlations Between Characteristics of Mean Light Curves of Long Period Variables 85 Andronov, I. L., and V. I. Marsakova “Asymptotic Parabola” Fit for Light Curves 198 Anon. Acknowledgements 13 Author Index 288 Errata: Hazen, Vol. 32, p. 141 525 Errata: Szkody, Homer, and Henden, Vol. 35, p. 307 525 Errata: Walker, Vol. 34, p. 287 525 Errata: Williams, Vol. 35, p. 317 525 Group photograph of the 86th Meeting of the AAVSO, Sion-St.-Luc, Switzerland, May 26–31, 1997 ii Index to Volume 35 470 List of Participants 15 Meeting Hosts, Local Organizing Committee, Scientific Organizing Committee, and Meeting Co-Sponsors 14 Table of Contents for Variable Stars: New Frontiers (86th Spring Meeting of the AAVSO) 2 Appenzeller, I., in H.
    [Show full text]